I have a thick scar on my shoulder (technically a keloid) and people often think I had shoulder surgery. I tell everyone that it's from a really bad gymnastics accident, but the real story is much more mundane.

In my old gym, we had to rip up the old floor boards and I was frustrated with how slowly we were lifting the boards. I decided to push my piece of the board up faster and it snapped. A piece of wood came down and cut my shoulder. I decided not to take care of it, so I'd get a "sweet scar". Turns out that was a dumb idea.